It is narrated from Hazrat Anas (may Allah be pleased with him) that once, in the gathering of the Prophet (peace and blessings be upon him), two men sneezed. The Prophet (peace and blessings be upon him) replied to one of them (by saying "Yarhamukallah") and left the other. Someone asked, "Two men sneezed, you replied to one of them, why did you not reply to the other?" He said, "He had said 'Alhamdulillah' and the other had not said it."